Various characteristics are measured to evaluate radio frequency (RF) performance of a semiconductor device, e.g., a metal oxide semiconductor field-effect transistor (MOSFET). Important characteristics include maximum oscillation frequency (fMAX) and cut-off frequency (fT). The fMAX and fT are characteristics related to the operational frequency of a device. Specifically, fMAX is a characteristic at which the operational frequency is evaluated in terms of electric power, and the fT is characteristics at which the operation frequency is evaluated in terms of electric current.
FIG. 1 is a view illustrating a semiconductor device 20 mounted over a substrate 10 having a ground signal ground (GSG) electrode structure. FIG. 2 is a plan view illustrating a finger type electrode structure of the semiconductor device 20. To improve fMAX and fT in RF applications, as shown in FIGS. 1 and 2, the semiconductor device is manufactured with a finger type structure.
Referring to FIG. 1, six electrodes 11-1 to 11-4, 12-1, and 12-2 are formed over the substrate 10. The four electrodes 11-1 to 11-4, which are formed at four corners of the substrate, respectively, are used as ground electrodes. The two electrodes 12-1 and 12-2, which are located between the corresponding ground electrodes, are used as signal electrodes.
The ground electrodes 11-1 to 11-4 and the signal electrodes 12-1 and 12-2 are connected to each other via conductive patterns 13 and 14. The semiconductor device 20 is mounted over the center of the substrate 10 such that the semiconductor device 20 is electrically connected to the conductive patterns 13 and 14.
Referring to FIG. 2, the semiconductor device 20 is constructed with the bodies of four electrodes 21, 22, and 23 disposed around an active region 24. Finger type electrodes diverge from the bodies of the respective electrodes 21, 22, and 23 into the active region 24. The two source electrodes 21 are formed at opposite sides of the active region 24. Fingers 21-1 of the source electrodes 21 and fingers 22-1 of the drain electrode 22 are alternately disposed between fingers 23-1 to 23-4 of the gate electrode 23.
The two ground electrodes 11-1 and 11-2 located at the upper side of the substrate 10 shown in FIG. 1 are bonded to the upper source electrode 21 of the semiconductor device 20. The two ground electrodes 11-3 and 11-4 located on the lower side of the substrate 10 are bonded to the lower source electrode 21 of the semiconductor device 20. The gate electrode 23 of the semiconductor device 20 is bonded to the left signal terminal 12-1 of the substrate 10. The drain electrode 22 of the semiconductor device 20 is bonded to the right signal terminal 12-2 of the substrate 10.
However, in the structure of each finger electrode of the semiconductor device 20, a single metal line diverges from the corresponding body, limiting improvements in RF performance, i.e., fMAX and fT.